Window tinting, sometimes also called window film, is typically a transparent plastic film or metallic laminate which is applied directly to glass windows. It is typically available in many different compositions. Further, varying effects on the optical and mechanical properties of the underlying glass are, also available. Most often, window tinting is applied to finished glass which is easier to install and less costly than chemically altered specialty glass. Applying various forms of window tinting to the glass windows in automobiles is a popular option on many vehicles.
The colorful film on these windows gives the vehicle a unique appearance while providing privacy and protection from the ultra-violet waves and the like. Heat rejection films are normally applied to the interior of flat glass windows to reduce the amount of infrared visible light, and UV radiation entering windows. Such films are either dyed or metalized (which can be transparent to visible light) to convert incoming solar radiation to infrared radiation, which is then rejected back through the glass to the exterior. Privacy films for automobiles are available in gradients of darkness, with the darker tints commonly known as “limo tint”.
Amongst the benefits of tinting windows in a vehicles (e.g., privacy, protection from sunlight), specific drawbacks exists that are unique to a vehicle. Due to its very nature, window tinting often reduces visibility through the vehicle's windows. This can be problematic at night, when motorists must be able to see through the windows of other vehicles in order to spot hazards which would otherwise be obstructed. Police officers also want to be able to identify the passengers in a vehicle. As a result, in many jurisdictions, there are laws to ensure darkness of films do not present a danger to motorists.
For example, in the United States, the federal Department of Transportation (DOT) specifies a minimum of 70% visible light transmission (VLT) for window tinting on the windshield and the windows to the immediate left and right of the driver for all commercial vehicles. The DoT does not specify any VLT requirements for any other windows, however, individual states can pass laws that go further than the requirements set forth by the DoT. Thus, in some jurisdictions, commercial vehicles may not have any window tinting. Just the opposite though, private vehicles may have tint on the windows to the immediate left and right of the driver as dark as 20% VLT, depending on the state.
With any number of variances across jurisdictions as well as variances in level of sunlight or desired privacy, choosing a single level of window tinting for each window in a vehicles limits the versatility of such a window tinting system. That is, one may wish to have a vehicle with little or no window tinting while driving at night yet have the same vehicle with a high level of window tinting for daytime driving when the sun is prevalent. What is needed is a system that allows options for various level of tinting on each window in a vehicle.